This study proposes a new method named the IIS-map-based method for analyzing interactions in face-to-face collaborative learning settings. This analysis method is conducted in three steps: firstly, drawing an initial IIS-map according to collaborative tasks; secondly, coding and segmenting information flows into information items of IIS; thirdly, computing attributes of information flows and analyzing relationships between attributes and group performance. An example illustrates how the methodology uncovers the interaction process based on information flows. The empirical study aims to validate the effectiveness of this method through thirty groups' interactions. The result indicates that quantity of activation of the targeting knowledge network can predict group performance and the IIS-map-based analysis method can analyze interactions effectively. The primary contribution of this paper is the methodology for analysis of interactions based on information flows. (Contains 8 figures and 4 tables.)